Constant surveillance alarm system for a plurality of remote locations



SYSTEM FOR CATIONS 1966 LLANCE ALARM Y OF REMOTE LO Filed Aug. 11,

- P. A. scHuM'ANN CONSTANT SURVEI A PLURALIT m v .I 8 3 v v mwm L 8 m Nmy 7 3 Tn w- 3N qww (3N 0N m mow 4 m (om \1 4 HM MM My 7 5 2 Q 'May 27,1969 PAUL A SCHUMANN 1 7 BY 075w;

A'rromm United States Patent US. Cl. 340213.1 11 Claims This inventionrelates generally to surveillance alarm systems and more particularly toa solid state system for monitoring a plurality of remotely locatedalarm condition sensing means which are generally placed at variousremote locations and in which signals therefrom are transmitted to acentrally located control station.

It is an object of the present invention to arrange a constantsurveillance alarm system in novel circuitry employing a minimum numberof indicating lights and a minimum number of conductors for connectingthese lights with the alarm contacts.

It is another object of the present invention to provide a solid stateconstant surveillance alarm system which will reduce the comparativesize of the equipment and further reduce the number of requiredcomponents.

Still another object of the present invention is to provide a constantsurveillance alarm system which utilizes the characteristics ofsemi-conductor devices such as controlled rectifiers for reducing sizeand increasing reliability.

The present invention has a further object in that a constantsurveillance system for monitoring a plurality of remotely locatedpoints at a central control station utilizes silicon controlledrectifiers as active elements.

In practice, the present invention contemplates monitoring one or morezones which are remotely located from a central station with each zonehaving a plurality of monitoring or alarm points including alarm contactmeans which are responsive to an alarm condition for providing anelectrical signal in accordance therewith. Semiconductor switch means inthe form of a semiconductor controlled rectifier, hereinafter referredto as an SCR, is coupled to each alarm point and is adapted to betriggered into conductivity when a signal is received from itsrespective alarm point and a supply voltage is simultaneously suppliedthereto by means of a zone switch coupled to a source of power supplypotential. Each alarm point of a zone, moreover, is commonly coupled toa zone alarm circiut including a zone .alarm light located at thecentral control station for providing an indication that an alarmcondition has occurred in a particular zone. Commonly coupled to each ofthe zone alarm circuits is another SCR and a gated oscillator circuitcontrolled by such SCR to provide a blinking condition to the particularzone alarm light which is responding to an alarm condition. Also anaudible alarm and a visual indication is provided which will indicatethat an alarm condition has occurred generally. Still another SCR isrespectively coupled to each zone alarm circuit providing a steady statealarm indication when an alarm acknowledgment switch is manually closed.Upon actuation of the particular zone switch, an alarm point light willindicate the respective alarm point in a particular zone due to thetriggering of the SCR coupled thereto. An additional feature is providedwhereby a test circuit is included for selec tively energizing all ofthe indicating alarm lights for ascertaining the operability thereof.

Other objects and advantages of the invention will become apparent froma study of the following description considered in conjunction with theaccompanying drawing wherein the single figure is a schematic electricaldiagram of an alarm system embodying the present inven tion.

In describing the operation of the system, it is assumed that initiallyall of the alarm contacts are in their illustrated condition, that allof the semiconductor elements are non-conductive, and that all of thealarm indicating lights are deenergized.

Considering the drawing, reference characters A, B and C generallyidentify circuitry for separate surveillance zones A, B and C eachhaving one or more monitoring or alarm contacts A1, A2, A3, A4 and B1,B2, etc., being in the form of either a normally open or a normallyclosed pair of contacts. One side of all contacts are commonly connectedto the positive terminal of a DC. power supply 10 by means of arespective power buss 12A, 12B and 12C. The opposite terminal of thenormally closed contact 1A is coupled to the base of transistor 14Awhile the opposite contacts of the normally open alarm contacts 2A, 3Aand 4A are coupled to the gate electrode of a respective SCR and asemiconductor diode. In greater detail, considering zone A, the alarmcontacts 1A are coupled to the base of transistor 14A which in turn hasits emitter coupled to buss 16A that is adapted to be connected to thepositive terminal of the DC. power supply 10. The base of transistor 14Aadditionally has a resistor 18A coupled to a point of referencepotential by means of a ground buss 19A which is returned to thenegative terminal of the power supply 10. The collector of transistor14A is coupled to the gate of SCR 21A by means of resistor 22A and theanode of semiconductor diode 30A. The normally open alarm contacts 2Aare coupled to the gate of SCR 23A by means of resistor 24A. Likewise,field alarm contacts 3A and 4A are coupled to the respective SCRs 25Aand 27A by means of resistors 26A and 28A (not shown). Also coupled tothe field alarm contacts 2A through 4A are the respective anodes ofsemiconductor diodes, 32A, 34A and 36A (not shown). The cathodes of thediodes 30A, 32A, 34A and 36A are commonly connected to an output line38A which in turn is connected to the zone alarm light LA.

The cathodes of SCRs 21A, 23A, 25A and 27A are commonly connected tobuss 20A which is adapted to be coupled to the negative terminal of theDC. power sup ply 10 through a zone switch SA (zone A). The anode of theSCRs 21A, 23A, 25A and 27A are connected in series to respective alarmpoint lights P1, P2, P3 and P4, which are commonly returned to thepositive terminal of the DC. power supply 10 by means of the line 40.

The circuitry with respect to zones B and C is chosen for sake ofexample to besubstantially identical with the circuitry shown withrespect to zone A. Thus, the output line 38B is connected to the zonealarm light LB and the output line 38C is connected to the zone alarmlight LC. It should also be noted that the corresponding SCRs 21B and210 (not shown), have their anodes commonly connected to the indicatorlight P1 by means of the circuit lead 42. Likewise, the SCRs 23B and 230are commonly coupled to the indicator light P2 by means of the circuitlead 44. Circuit leads 46 and 48 commonly connect SCRs 25B and 25C, and27B and 270, respectively.

The indicator lights P1 through P4 will then present an indication of aparticular alarm point within a zone whereas the zone alarm lights LA,LB and LC give an indication of the particular zone. Seven indicatorlights then are adapted to provide twelve indicators for twelve alarmpoints.

Zone alarm circuitry is also associated with the zone alarm lights LA,LB, and LC. Each zone alarm light LA, LB and LC is connected in seriesto silicon controlled rectifiers 50A, 50B and 50C, respectively. Alsoassociated with the aforesaid zone alarm lights is a gated free-run- 3ning multivibrator circuit 52 and another silicon controlled rectifier54. Considering the zone alarm light circuitry for LA in greater detail,a resistance capacitor combination comprising capacitor 56A and 58A arecoupled in series between the output line 38A and the age of SCR 54. Thezone alarm light LA is connected in series to the anode of SCR 50A whileits cathode is returned to ground which is commonly connected with thecathode of SCR 54. The gate electrode of SCR 50A is coupled to the oneset of two sets of normally open contacts of an alarm acknowledge switchSW through the resistor 60A. A resistor 62A is coupled from the commonconnection of capacitor 56A and the light LA to ground. A semiconductordiode is coupled from the common connection of the light LA and theanode of SCR 50A to the collector of transistor T1 of the multivibratorcircuit 52.

The circuitry with respect to zone alarm lights LB and LC is similarwith respect to that described to zone light LA. However, it should benoted that the resistors 60A, 60B and 60C are commonly connected to thesaid one set of contacts of the alarm acknowledge switch SW by means ofcircuit lead 66. The diodes 64A, 64B and 64C have their cathodescommonly connected to the collector of transistor T1 by means of circuitlead 68. Also, the resistors 58A, 58B and 58C are commonly connected tothe gate of SCR 54 by means of circuit lead 70. A capacitor 59 iscoupled between the gate of SCR and ground.

A semiconductor diode 72A is coupled from the zone output line 38A tothe multivibrator circuit 52 at the common connection of resistors 74,75 and 76. Semiconductor diode 72B is connected between the zone outputlead 38B to the multivibrator circuit 52 and diode 72C is connected fromthe multivibrator circuit 52 to the zone output lead 38C. The anode ofSCR 54 is connected to the common connection between the emitters oftransistors T1 and T2. It should be pointed out that the other set ofcontacts of the alarm acknowledge switch SW, which is also shown in anormally open position, is coupled across SCR 54.

An audible alarm device 78 is coupled across the multivibrator circuit52 such that one side thereof is common to the emitters of transistor T1and T2 while the other side is common to the diodes 72A, 72B and 72C. Avisual alarm 80 is also coupled directly across the audible alarm 78 forbeing indicative of an alarm condition generally as is the audiblealarm.

A test circuit for the above described circuitry includes a double polenormally open switch ST and seven semiconductor devices, i.e., diodes82A, 82B and 82C, and diodes 84-1, 84-2, 84-3 and 84-4. One set ofcontacts of the switch ST when closed connects the negative terminal ofthe power suppply to the diodes 84-1 through 844. The cathodes of thesediodes are commonly connected to the aforementioned section of theswitch ST while the anodes thereof are respectively connected to thealarm point lights P1 through P4 respectively. By closing the switch ST,all four lights P1 through P4 will be lit since the opposite side of thelights are returned to the positive terminal of the power supply 10. Theother set of switch contacts of the switch ST is connected on one sideto the positive terminal of the power supply 10 with the outer sidebeing commonly connected to the zone output line 38A which is common tothe capacitor 56A and the resistor 62A and the zone alarm light LA.Similarly, the cathode of diode 82B is connected to the zone output line38B and the cathode of diode 82C is connected to the zone output line380.

The operation and further description of the embodiment shown on thedrawing will be accomplished by describing the operation of the circuitwhen an alarm condition occurs at a selected point in a zone. Assumingalarm point 2 of zone A identified as the normally open alarm contacts2A has closed indicating an alarm condition, the positive side of thepower supply 10 is applied to the anode of the diode 32A as well as thegate of SCR 23A by means of the buss 12A. SCR 23A however, will not betriggered inasmuch as the ground return circuit coupling the cathode tothe negative terminal of the power supply A is open-circuited due to thenormally open condition of the zone switch SA. Diode 32A, on the otherhand, becomes conductive and the positive voltage on buss 12A isimpressed on the zone output line 38A. The appearance of a positivepotential at the zone output line 38A renders diode 72A conductiveapplying a positive potential to the anode of SCR 54 which may be calledthe alarm SCR, via the audible alarm 78 and the light 80 connected inparallel. At the same time, a transient current signal is established bythe closure of the alarm point contacts 2A and is fed to the gate of thealarm SCR 54 by means of the triggering circuit including the capacitor56A and the resistor 58A. The transient signal thus applied to the gateof SCR 54 triggers it into conduction placing line 83 at groundpotential completing the circuit necessary for operating the audiblealarm 78, the indicator lamp 80, and also the free-running multivibratorcircuit 52.

It should be noted that the collector load impedance for transistors T1is any one or all of the zone alarm lights LA, LB and LC, which iscommonly connected to the collector thereof by means of respective diode64. In other words, when a positive voltage appears on any zone outputline, such as line 38A, zone alarm light LA becomes the load impedancefor the transistor T1 inasmuch as blocking diode 64A is properly poledto conduct. The normal operation of the free-running multivibratorcircuit, such as shown in circuit 52 is such that one transistor T1 orT2 will conduct while the other transistor is turned ofif. The firsttransistor will then be turned oh. when the other transistor is turnedon. The zone alarm indicating light, in the specific example LA, whichforms a part of the multivibrator circuit is energized each timetransistor T1 is turned on during operation of the multivibrator. Thefrequency of the operation of the multivibrator 52 is low enough so theon and off operation of the transistor T1 can be detected by the eye asthe alarm indicating of an alarm condition occurring in Zone A. Not onlyis there a blinking indication that an alarm has occurred in zone A butthe audible alarm 78 gives an audible indication that an alarm conditionexists generally as well as visual indication thereof as provided by thelamp 80.

When an alarm condition occurs, the alarm acknowledge switch SW ismomentarily closed by the operator which places a short across the SCR54 rendering it nonconductive and simultaneously places the positiveterminal of the power supply 10 on line 66, which in turn appliespositive voltage to the gates of the SCRs 50A, 50B and 50C through theirrespective gate resistors 60A, 60B and 60C. Since in the example underconsideration only zone output line 38A has a positive voltage thereon,SCR 50A will be triggered into conduction causing the zone alarm lightLA to be continuously energized due to the fact that the return path toground is provided through the SCR which now exhibits a very lowimpedance to ground.

Once the particular zone in which an alarm has been indicated isestablished, in the instant example zone A, it becomes desirable todetermine which alarm point is presenting an alarm condition. This iseifected by means of the zone switches SA, SB and SC in combination withthe SCR circuitry arrangement for each zone. The switch SA is used fordetermining the point at which an alarm has occurred in zone A, theswitch SB is used for determining the point at which an alarm occurs inzone B, and switch SC is used for determining the point at which analarm has occurred in zone C. Assuming that an alarm condition hasoccurred at alarm contacts 2A, closing zone switch SA will provide aground return over line 20A for the SCRs 21A, 23A, 25A and 27A. Each ofthese SCRs has positive voltage applied to their respective anodesthrough their respective indicator lights P1 through P4. Since thecontacts 2A are now closed, a positive potential will be applied to thegate of transistor 23A rendering it conductive, thereby closing thecircuit through light P2 causing it to light and thereby providing anindication of an alarm condition at alarm point 2A. SCRs 21A, 25A and27A will remain non-conductive as well as all of the SCRs in zones B andC.

A separate alarm circuit for each zone is supplied in order that thealarm SCR 54 can be triggered by an alarm condition from any zone andafter being acknowledged can be triggered by an alarm conditionoccurring in a different zone. Also, when the second alarm isacknowledged, SCR 54 can be triggered by an alarm condition occurring instill another zone, etc.

After an alarm condition is corrected, it is necessary that thecapacitor in the zone alarm circuit, i.e., capacitors 56A, 56B and 57C,associated with the zone havingaan alarm condition be discharged. Thisis necessary in order to again place the circuit in condition forreceiving an alarm signal from the respective zone. The subjectcapacitor in the triggering circuit is discharged by means of therespective resistor 62A, 62B or 62C connected from the capacitor toground.

When it is desirable to utilize normally closed alarm contacts in thesystem such as, at alarm point 1A, an additional circuit element isneeded for each set of normally closed contacts. This element takes theform of transistor 14A coupled between the alarm point contacts 1A andthe blocking diode 30A. The normally closed contacts 1A operate to holdthe transistor 14A in an ofi or non-conductive condition. When thecontacts 1A open, however, transistor 14A is rendered conductive andsince the emitter-tdcollector resistance is negligible when operated inthe switching mode, positive voltage appears on zone output line 38Afrom buss 16A via transistor 14A and blocking diode 30A. In all otherrespects, the operation as hereinbefore described is the same.

As indicated previously, a test circuit for the preferred embodimentincludes the test switch ST in combination with the diodes 84-1 through84-4 and diodes 82A through 82C. The test circuit when operated by meansof closing the switch ST, applies the positive voltage of the powersupply to each of the alarm indicating lamps LA, LB and LC by means ofdiodes 82A, 82B and 82C, respectively, as well as to the audible alarm78, lamp 80 and the multivibrator circuit 52 by means of the diodes 72A,72B and 72C. The alarm SCR 54 is triggered by the transient produced byclosing the switch ST causing the multivibrator 52, the alarm indicatinglamps and the audible alarm 78 to operate. In addition, the circuitryapplied a ground connection to all of the alarm point lights P1 throughP4 by means of the diodes 84-1 through 84-4 providing an indication asto whether or not they are operating properly. The diodes mentioned withrespect to the test circuitry moreover are used to keep the signal whichmay be presented during normal use of the system from passing to otherpoints in the circuit where it might cause an erroneous indication.

What has been shown and described therefore is a solid state constantsurveillance alarm system having a number of zones identified as A, B,C, etc. each having a number of monitoring or alarm points in the formof the alarm contacts. The number of zones and the number of monitoredpoints have been selected for the sake of brevity it being understoodthat any larger suitable number of such zones and/or points may be used.One side of each of the contacts in a given zone is connected via adiode to a common output line for the zone. The output line for a zoneis connected to a zone alarm light LA, LB, LC, etc. at a centralmonitoring station or control center and then to ground. The oppositeside of all the cont-acts in a zone is connected to the positive side ofa DC. power supply. Should one or more of the monitoring points in azone indicate an alarm condition, the zone indicator or alarm light willbe energized. A circuit for each zone for controlling the energizationof an audible alarm is also provided and is effected to energize theaudible alarm when an alarm condition exists in the zone. The zone alarmindication is by means of a blinking light provided by a gatedmultivibrator circuit which is rendered operative by means of an alarmSCR which is triggered by a transient coupled thereto from the alarmpoint unless an alarm condition exists. When an alarm is acknowledged bymeans of an alarm acknowledge switc an SCR in circuit combination withthe alarm zone light is triggered rendering it energized in a steadystate condition. When the zone has been determined, a zone switch isclosed which permits another SCR to be triggered into conductionenergizing an alarm point light, thus giving indication not only of aparticular zone but the particular point at which an alarm conditionexists.

What is claimed is:

1. A constant surveillance alarm system in which a plurality of remotezones are electrically monitored from a central monitoring stationcomprising in combination:

a source of supply voltage;

at least one alarm sensing means located in each of said plurality ofremote zones and being operable in response to an alarm condition tochange operating states and including circuit means for coupling asupply voltage to one side of said alarm sensing means from said sourceof said supply voltage;

a zone alarm coupled to said at least one alarm sensing means including,

first semiconductor switch means coupled to the other side of said alarmsensing means in each zone and also to said source of supply voltage soas to be rendered conductive upon the occurrence of an alarm condition,

relaxation oscillator circuit means coupled between said other side ofsaid alarm sensing means and said first semiconductor switch means so asto become oper able by application of said supply voltage thereto whensaid first semiconductor switch means becomes conductive,

first alarm indicator means for each zone of said plurality of remotezones coupled between said other side of said alarm sensing means ineach zone and said relaxation oscillator circuit forming a portion ofthe load circuit thereof so as to be intermittently energized upon theoccurrence of an alarm condition in the respective zone by operation ofthe relaxation oscillator circuit,

second semiconductor switch means coupled to each of said firstindicator means, and

switch means coupled to said first semiconductor switch means and saidsecond semiconductor switch means which when activated renders saidfirst semiconductor switch means non-conductive and renders said secondsemiconductor switch means conductive when an alarm condition exists inthe respective zone to continuously energize said first alarm indicatormeans; and

an alarm point circuit for each zone including,

third semiconductor switch means coupled to the other side of said alarmsensing means and being responsive thereto to become conductive when asupply voltage is applied thereto and the respective alarm sensing meanschanges operating states,

a second alarm indicator means coupled between said source of supplyvoltage and said third semiconductor switch means becoming energizedwhen said third semiconductor switch means becomes conductive, and

another switch means coupled between said source of supply voltage andsaid third semiconductor switch means for selectively applying a supplyvoltage thereto, said third semiconductor switch means becomingconductive thereby when an alarm condition exists at said alarm sensingmeans whereby said second alarm indicator means is energized.

2. A constant surveillance alarm system as claimed in claim 1 whereinsaid first, second and third semiconductor switch means are comprised ofsemiconductor controlled rectifiers.

3. The invention as defined by claim 1 wherein a plurality of alarmsensing means are located in each of said plurality of remote zones.

4. A constant surveillance alarm system as defined by claim 1 andadditionally including an audible alarm circuit coupled between saidother side of said alarm sensing means and said first semiconductorswitch means, being rendered operative when said first semiconductorswitch means becomes conductive to present an audible alarm of an alarmcondition existing generally Without respect to zone location or aspecific alarm point in said zone.

5. The invention as defined by claim 1 wherein said at least one alarmsensing means comprises a pair of alarm contacts responsive to an alarmcondition to change from a first operating state to a second operatingstate.

6. The invention as defined by claim 1 wherein said relaxationoscillator means comprises a multivibrator circuit and including meansfor being gated into operation by said first semiconductor switch meansso as to become operable when said first semiconductor switch means istriggered into conduction when an alarm condition exists.

7. A constant surevillance alarm circuit as defined by claim 1 whereinsaid first alarm indicator means and said second alarm indicator meanscomprise indicator lights which are selectively energized in response toan alarm condition existing in a zone and upon actuation of said anotherswitch means indicates a particular point in a specified zone.

8. A constant surveillance alarm system as claimed in claim 1 whereinsaid at least one alarm sensing means comprises a normally closed set ofalarm contacts and transistor means biased in a normally non-conductivecondition being coupled between said other side of said alarm sensingmeans and said zone alarm circuit.

9. The invention as defined by claim 1 wherein said at least one alarmsensing means comprises a set of normally open alarm contacts.

10. A constant surveillance alarm system as defined by claim 1 andadditionally including circuit means for determining the operability ofsaid first and second alarm indicator means comprising: a firstplurality of semiconductor diodes having one side thereof coupled to oneside of said first alarm indicator means; switch means coupling theother side of said first plurality of semiconductor diodes to a terminalof said source of supply voltage; a second plurality of semiconductordiodes having one side thereof coupled to one side of said second alarmindicator means; second switch means coupling the other side of saidsecond plurality of semiconductor diodes to a terminal of said source ofsupply voltage, and said first and said second switch means when closedproviding a closed electrical circuit for energizing said first and saidsecond alarm indicating means from said source of supply voltage.

11. A constant surveillance alarm system in which a plurality of remotezones are electrically monitored from a central station comprising incombination:

a source of supply voltage;

a plurality of alarm contacts selectively located in each of saidplurality of remote zones and being responsive to an alarm condition tochange from a first operating state to a second operating state;

circuit means for coupling a supply voltage from said source of supplyvoltage to one side of all said plurality of alarm contacts;

a zone alarm circuit coupled to the other side of each said plurality ofalarm contacts in each of said plurality of remote zones and comprisingfirst controlled rectifier means responsive to an alarm condition in anyof said plurality of alarm contact means, a zone alarm light adapted tobe energized from said source of supply voltage when said firstcontrolled rectifier means becomes conductive, second controlledrectifier means coupled in series to said zone alarm light for renderingsaid alarm light continuously energized upon the occurrence of an alarmcondition in the respective zone; and

an alarm point indicating circuit coupled to the other side of each saidplurality of alarm contacts for indicating a particular point wherein analarm condition occurs within a specific zone comprising a thirdcontrolled rectifier means coupled to each of said plurality of alarmcontacts, circuit means energized by means of said respective alarmcontacts upon the occurrence of an alarm condition, switch meanscoupling each of said third controlled rectifier means to said source ofsupply voltage for rendering said each third controlled rectifier meanscapable of being energized by said alarm contacts when said switch meansare closed, and an alarm light coupled to each said third controlledrectifier means for indicating the point at which an alarm conditionoccurs in a specific zone.

References Cited UNITED STATES PATENTS 2,895,125 7/1959 Watts 340-22712,917,731 12/1959 Rodgers 340213.1 3,381,286 4/1968 Walsh 340213.1

JOHN W. CALDWELL, Primary Examiner.

P. PALAN, Assistant Examiner.

US. Cl. X.'R.

1. A CONSTANT SURVEILLANCE ALARM SYSTEM IN WHICH A PLURALITY OF REMOTEZONES ARE ELECTRICALLY MONITORED FROM A CENTRAL MONITORING STATIONCOMPRISING IN COMBINATION: A SOURCE OF SUPPLY VOLTAGE; AT LEAST ONEALARM SENSING MEANS LOCATED IN EACH OF SAID PLURALITY OF REMOTE ZONESAND BEING OPERABLE IN RESPONSE TO AN ALARM CONDITION TO CHANGE OPERATINGSTATES AND INCLUDING CIRCUIT MEANS FOR COUPLING A SUPPLY VOLTAGE TO ONESIDE OF SAID ALARM SENSING MEANS FROM SAID SOURCE OF SAID SUPPLYVOLTAGE; A ZONE ALARM COUPLED TO SAID AT LEAST ONE ALARM SENSING MEANSINCLUDING, FIRST SEMICONDUCTOR SWITCH MEANS COUPLED TO THE OTHER SIDE OFSAID ALARM SENSING MEANS IN EACH ZONE AND ALSO TO SAID SOURCE OF SUPPLYVOLTAGE SO AS TO BE RENDERED CONDUCTIVE UPON THE OCCURRENCE OF AN ALARMCONDITION, RELAXATION OSCILLATOR CIRCUIT MEANS COUPLED BETWEEN SAIDOTHER SIDE OF SAID ALARM SENSING MEANS AND SAID FIRST SEMICONDUCTORSWITCH MEANS SO AS TO BECOME OPERABLE BY APPLICATION OF SAID SUPPLYVOLTAGE THERETO WHEN SAID FIRST SEMICONDUCTOR SWITCH MEANS BECOMESCONDUCTIVE, FIRST ALARM INDICATOR MEANS FOR EACH ZONE OF SAID PLURALITYOF REMOTE ZONES COUPLED BETWEEN SAID OTHER SIDE OF SAID ALARM SENSINGMEANS IN EACH ZONE AND SAID RELAXATION OSCILLATOR CIRCUIT FORMING APORTION OF THE LOAD CIRCUIT THEREOF SO AS TO BE INTERMITTENTLY ENERGIZEDUPON THE OCCURRENCE OF AN ALARM CONDITION IN THE RESPECTIVE ZONE BYOPERATION OF THE RELAXATION OSCILLATOR CIRCUIT, SECOND SEMICONDUCTORSWITCH MEANS COUPLED TO EACH OF SAID FIRST INDICATOR MEANS, AND SWITCHMEANS COUPLED TO SAID FIRST SEMICONDUCTOR SWITCH MEANS AND SAID SECONDSEMICONDUCTOR SWITCH MEANS WHICH WHEN ACTIVATED RENDERS SAID FIRSTSEMICONDUCTOR SWITCH MEANS NON-CONDUCTIVE AND RENDERS SAID SECONDSEMICONDUCTOR SWITCH MEANS CONDUCTIVE WHEN AN ALARM CONDITION EXISTS INTHE RESPECTIVE ZONE TO CONTINUOUSLY ENERGIZE SAID FIRST ALARM INDICATORMEANS; AND AN ALARM POINT CIRCUIT FOR EACH ZONE INCLUDING, THIRDSEMICONDUCTOR SWITCH MEANS COUPLED TO THE OTHER SIDE OF SAID ALARMSENSING MEANS AND BEING RESPONSIVE THERETO TO BECOME CONDUCTIVE WHEN ASUPPLY VOLTAGE IS APPLIED THERETO AND THE RESPECTIVE ALARM SENSING MEANSCHANGES OPERATING STATES, A SECOND ALARM INDICATOR MEANS COUPLED BETWEENSAID SOURCE OF SUPPLY VOLTAGE AND SAID THRID SEMICONDUCTOR SWITCH MEANSBECOMING ENERGIZED WHEN SAID THIRD SEMICONDUCTOR SWITCH MEANS BECOMESCONDUCTIVE, AND ANOTHER SWITCH MEANS COUPLED BETWEEN SAID SOURCE OFSUPPLY VOLTAGE AND SAID THIRD SEMICONDUCTOR SWITCH MEANS FOR SELECTIVELYAPPLYING A SUPPLY VOLTAGE THERETO, SAID THIRD SEMICONDUCTOR SWITCH MEANSBECOMING CONDUCTIVE THEREBY WHEN AN ALARM CONDITION EXISTS AT SAID ALARMSENSING MEANS WHEREBY SAID SECOND ALARM INDICATOR MEANS IS ENERGIZED.